To compare open a text file and click set as first to compare in Plugins>compare>set as first to compare. You can access the plugin from Plugins>Compare.

Notepad++ restarted and the plugin is installed. The Plugins Admin windows will be displayed, search or look for compare select the plugin and click install. You can install the comparison plugin, go to Notepad++ menu, Plugins>Plugins Admin. A comparison plugin is available for Notepad++ editor that offers a side-by-side visual differencing.

Notepad++ supports around 80 programming languages with syntax highlighting and code folding. Notepad++ is a free notepad, text editor and source code editor. It also provides advanced XML-aware differencing and editing capabilities. This easy diff merge tool lets you quickly compare and merge text or source code files, synchronize directories, and compare database schemas and the contents of database tables via its straightforward visual interface. One can use it for diff or merge files, directories, and database schemas and tables. Altova DiffDog is a compare and merges tool.

Text compare online tools